ChemWhiz ReferenceFundamentals
SI Prefixes and Unit Conversions
Complete table of SI (metric) prefixes from quecto to quetta, with conversion factors and common chemistry applications.
01Use this when
Converting between metric units in dimensional analysis (nm ↔ m, mL ↔ L, kJ ↔ J).
02Conditions
Each prefix is a power of ten; the SI base unit of mass is the kilogram.
03Watch out
Orient the conversion factor so the unit you are removing cancels; do not invert the power.
SI Prefixes from Quetta to Quecto
Multiply by the factor to convert a prefixed unit to the base unit; divide to go back.
25 of 25
| quetta | Q | 1030 | 1,000,000,000,000,000,000,000,000,000,000 | |
| ronna | R | 1027 | 1,000,000,000,000,000,000,000,000,000 | |
| yotta | Y | 1024 | 1,000,000,000,000,000,000,000,000 | |
| zetta | Z | 1021 | 1,000,000,000,000,000,000,000 | |
| exa | E | 1018 | 1,000,000,000,000,000,000 | |
| peta | P | 1015 | 1,000,000,000,000,000 | |
| tera | T | 1012 | 1,000,000,000,000 | TBq (terabecquerel) — radioactivity |
| giga | G | 109 | 1,000,000,000 | GHz — spectroscopy frequencies |
| mega | M | 106 | 1,000,000 | MPa (megapascal) — high pressures |
| kilo | k | 103 | 1,000 | kJ (kilojoule) — enthalpy changes; kg (kilogram) — SI base unit of mass |
| hecto | h | 102 | 100 | |
| deca | da | 101 | 10 | |
| — | — | 100 | 1 | Base unit (meter, gram, liter, mole) |
| deci | d | 10-1 | 0.1 | dL (deciliter) — medical blood tests |
| centi | c | 10-2 | 0.01 | cm (centimeter) — common lab measurements |
| milli | m | 10-3 | 0.001 | mL (milliliter) — lab volumes; mmol — millimoles |
| micro | μ | 10-6 | 0.000001 | μg (microgram) — trace element amounts; μM — micromolar |
| nano | n | 10-9 | 0.000000001 | nm (nanometer) — wavelengths of light (visible: 400–700 nm) |
| pico | p | 10-12 | 0.000000000001 | pm (picometer) — atomic radii (H = 53 pm) |
| femto | f | 10-15 | 0.000000000000001 | fm (femtometer) — nuclear radii |
| atto | a | 10-18 | 0.000000000000000001 | attosecond — electron orbital timescales |
| zepto | z | 10-21 | 0.000000000000000000001 | |
| yocto | y | 10-24 | 0.000000000000000000000001 | Mass of a proton ≈ 1.67 yg |
| ronto | r | 10-27 | 0.000000000000000000000000001 | |
| quecto | q | 10-30 | 0.000000000000000000000000000001 |
Important Notes
- The SI base unit of mass is the kilogram (kg), the only base unit with a prefix.
- In chemistry, the most commonly used prefixes are kilo (k), centi (c), milli (m), micro (μ), nano (n), and pico (p).
- To convert: multiply by the factor when going from prefixed to base unit, divide when going from base to prefixed.
- 1 Å (angstrom) = 100 pm = 0.1 nm. Angstroms are commonly used for bond lengths but are not an SI unit.
- Avogadro's number (6.022 × 1023) is close to the yotta prefix (1024), which is why 1 mole works as a practical laboratory quantity.
- Quetta (Q), ronna (R), ronto (r), and quecto (q) were added to the SI in 2022 (27th CGPM, Resolution 3) to name very large and very small quantities.
Verification references: SI prefix set per the 27th General Conference on Weights and Measures (CGPM, 2022, Resolution 3); BIPM SI Brochure.